At last Kell Brook has the fight that will define his career – whether he wins or loses.

Step up two divisions to defeat the seemingly invincible Gennady Golovkin in London tonight and he will have the victory on his record to match Tyson Fury over Wladimir Klitschko, Ricky Hatton versus Kostya Tszyu.

Gallantly lose a bout few expect him to prevail in, and the Sheffield boxer may finally win the hearts of the British public.

Because boxing is a funny old sport. Victory upon victory is not necessarily the key to adulation and a place in history as it is in other sports.

Great fights are what shape great fighters.

Think of Henry Cooper losing at the hands of Cassius Clay.

Of Frank Bruno, three times trying to win the world heavyweight title before finally landing it. Know what I mean?

Expand the analogy further and Joe Frazier is remembered more for two defeats to his great foe Muhammad Ali than he is for his victories.

The ‘four kings’ of the middleweight division of the 1980s – Sugar Ray Leonard, Marvin Hagler, Tommy Hearns and Roberto Duran – are immortalised in the boxing annals because of the wars they waged between themselves.

Kell Brook has won every professional fight he has contested – 36 in all – but he has not won the battle for the nation’s affections.

Not even his greatest victory, that over Shawn Porter in California two years ago to win the IBF world welterweight title, gave him the nationwide acclaim it warranted.

Subsequent fights against so-called ‘mandatory’ challengers like Jo Jo Dan and Kevin Bizier have not lived up to the billing.

Brook has longed for an opponent to really test the merits of his undefeated record, and finally he has got one, after accepting the challenge of Golovkin.

The 34-year-old from Kazakhstan has had the middleweight division running scared with his 35-0 record that brought with it the WBC and IBF world titles.

But the young man who was spotted by the godfather of Sheffield boxing, Brendan Ingle, and is trained by his son Dominic, will dive headlong into the fighter known as ‘GGG’ in the capital tonight.

Because the prize at stake is something Brook has craved, worldwide respect and noteriety.

Golovkin is the best pound for pound fighter in the world. Upset the odds tonight, and Brook enters a new stratosphere.

Brook insisted he could see “fear” in Golovkin’s eyes when they weighed in yesterday.

“I looked into his eyes, and I could see fear,” he said.

“He knows he’s in a real fight, Saturday night, and it can’t come quick enough, I’m ready for this moment.

“I just feel that he’s on edge, that he’s uncomfortable. I feel that it’s my time; he can see in my eyes that I want this fight. I want to shock the world. I’m at a natural, healthy weight and I can’t wait to show the world what I can do.”

Brook’s intense struggles to make the 147lbs welterweight limit were widely known, and often appeared to undermine his preparations. He looked impressive having weighed in at 159.4lbs, and he said: “I no longer look like I’ve got my grandad’s teeth in.

“It’s not as bad, this time. I’m smiling, happy, hydrated, ready to fuel up, get in and let some rocket launchers ago. I’ve done absolutely everything I could have done in training.

“I’m ready to put my chin, everything I’ve got, to the test Saturday night and ready to take that challenge.

He added: “Any fighter that laces a pair of gloves up, you can’t get any higher than beating the man that everyone’s fearful of, taking his titles away, in my own country.”